An ommnipresent problem which is met by designers of gas turbine engine turbine structures, is the relative thermal reaction characteristics of the parts which make up the turbine structure. Thus parts which are constructed from the same type of material may differ in thermal growth because some of the parts operate in a higher temperature than the remainder. Moreover, some of those parts may rotate at high speed, so that the centrifugal force which is generated aggrevates the differing rate of dimensional change between rotating and static parts.
Attempts have been made to construct an assembly of parts, wherein the material of some fixed parts have thermal reaction characteristics which differ from the rotating parts, so that, having regard to the local environment in which they work, they may expand and contract in a manner which is matched to the corresponding movements of the rotating parts. A drawback however, is that where parts which have differing thermal reaction characteristics are fixed together, unacceptable stresses are generated at the joint.